Pseudomonas aeruginosa: ecology, evolution, pathogenesis and antimicrobial susceptibility.

Pseudomonas aeruginosa has long served as a model organism in microbiology, particularly for studies on gene expression, quorum sensing, antibiotic resistance, virulence and biofilm formation. Its genetic tractability has advanced the understanding of complex regulatory networks and experimental evolution. The versatility of this bacterium stems from its genomic variability, metabolic flexibility and phenotypic diversity, enabling it to thrive in diverse environments, both as a harmless saprophyte and an opportunistic human pathogen. P. aeruginosa can cause acute and chronic human infections, particularly in patients with underlying immune deficiencies. Its intrinsic antibiotic tolerance and resistance, together with its ability to produce multiple virulence factors while rapidly adapting to infection conditions, pose a major clinical challenge. In this Review, we explore key features contributing to the ecological and pathogenic versatility of P. aeruginosa. We examine the molecular mechanisms and ecological and evolutionary implications of quorum sensing and biofilm formation. We explore the virulence strategies and in vivo fitness determinants, as well as the evolutionary dynamics and global epidemiology of P. aeruginosa, with a focus on antimicrobial resistance. Finally, we discuss emerging strategies to control P. aeruginosa infections and address outstanding questions in the field.